In one-time programmable (OTP) memory, which is a form of digital memory, the setting memory bits may be locked by using a fuse or an anti-fuse for each bit. Most OTP memories may require a programmable fuse element along with a select device (e.g., a switch). Anti-fuse cells may be implemented based on oxide breakdown, where a layer (e.g., a thin layer) of silicon oxide (SiO2) located between a gate terminal and a channel of a transistor (e.g., MOS transistor) may experience breakdown. The breakdown process can happen in a defective transistor, although in normal transistors, high temperature and/or high voltage can cause breakdown of the oxide layer. The oxide breakdown can also be utilized in a positive manner in non-volatile memory (NVM), as a memory cell can be programmed by trapping charges in an isolated location to be applied to break the oxide (only one time) at a program area.
An anti-fuse cell may also be implemented by using a thin silicon layer between two metal layers (e.g., metal tracks) as an insulator, which can upon applying a pulse of relatively high voltage and current be converted to a conducting poly-silicon. The poly-silicon that is grown on the spot can work as a link between the two metal layers. Further, the anti-fuse cells can be realized by using thick or split-oxide layers. The thin-oxide anti-fuse cells typically need a select device for proper operation, therefore, cannot be used in cross-point diode array configurations, as it can form an ohmic contact directly to the source instead of forming a diode connected transistor.